Efforts will be continued to improve the culture of urothelial cells in vitro, to characterize the cultured cells and original tumor cells by karyological analysis, and to examine them for evidence of association of oncornavirus by means of reverse transcriptase assay and molecular hybridization. The effects of certain chemical carcinogens on urothelial cells in vitro will be examined. BIBLIOGRAPHIC REFERENCE: A Comparative Study of Two Epithelial Cell Cultures with Different Growth Patterns. J. Vergara, P. Ingram, R. Bonar, G. Boyarski, and C. Reich. Scanning Electron Microscopy/1976: 113-119, 1976.